In ink jet printing systems a printed image is made up of individual droplets of ink generated at a nozzle and propelled towards a substrate. There are two principal systems: drop on demand where ink droplets for printing are generated as and when required; and continuous ink jet printing in which droplets are continuously produced and only selected ones are directed towards the substrate, the others being recirculated to an ink supply.
Continuous ink jet printers supply pressurized ink to a print head drop generator where a continuous stream of ink emanating from a nozzle is broken up into individual regular drops by, for example, an oscillating piezoelectric element. The drops are directed past a charging electrode where they are selectively and separately given a predetermined charging before passing through a transverse electric field provided across a pair of deflection electrodes. Each charged drop is deflected by the field by an amount that is dependent on its charging magnitude before impinging on the substrate whereas the uncharged drops proceed without deflection and are collected at a gutter from where they are recirculated to the ink supply for reuse. The charged drops bypass the gutter and hit the substrate at a position determined by the charging on the drop and a position of the substrate relative to the print head.
Proper alignment among the droplet generator, the nozzle, the charging electrode, the deflection electrodes, and the gutter are imperative in order to ensure that the ink droplets begin to travel along an intended course and any deflections are effected as intended. Conventional print heads include an adjustable mount for the charging electrode that permits adjustment of the print head alignment. This has been necessary to accommodate misalignments that frequently occur during operation and handling of the print head.